Its a big beast of a thing. They say in the manual that its is suitable to be undermount installed.

in fact here are the directions:
Please note that care must be taken to protect the surface of the tub
during all aspects of the installation. Do not drill or cut the bath deck with
the tub directly beneath it as damage to the tub may result.
1. Install the tub per the installation instructions provided with the unit.
2. Prepare the bath deck support structure per the local codes.
Note - the bath deck must be self supporting.
3. Cut bath deck to your specifications.
4. Place the bath deck in position and trace the opening on the tub with
a soft pencil. Do not drill or cut the bath deck with the tub directly
beneath it as damage to the tub may result.
5. Remove the bath deck and apply a generous bead of waterproof
sealant on the outer edge of the traced line.
6. Replace the bath deck and secure it into place.
7. Apply additional sealant along the tub and bath deck interface as
necessary to ensure a watertight seal.
8. Remove excess sealant per the manufacturer's instructionsFinished bath deck

I've got my frame built for the tub (no shower, just a soaking tub). and I was either thinking about building up the frame so that its even with the top of the tub, then securing a layer of durock over the deck AND tub lip, then tile that, or take a belt sander, sand down the finished top of the tub, buld my deck even, then just tile on the deck/tub directly.

the first way would be mroe secure for tile, but then I would have lip of durock on the inside of the tub that I would have to figure out out to tile, and the rounded curves in the corners could be tough.

tiling straight to the top would look better, but im not sure about tiling to even roughed up fiberglass. also, im Leary of doing that to my new tub.

I would not suggest putting the tile directly on the tub. I would go with your first idea and you can use quarter round tiles around the edge (like on the older kitchen sink counter tops). You may need to cut them shorter to make the oval curve. Also, you could use mosaic tiles (1"x1") to create the border and cover the backer board.